<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
  </head>

  <body>
    <div id="root">
      <!-- 不带小括号需要用到event对象 $event自动帮我们传递了-->
      <button @click="fn1">按钮1</button>
      <!-- 带小括号需要用到event对象 必须传递 $event -->
      <button @click="fn2($event)">按钮2</button>
      <!-- 带小括号需要用到event对象并且额外传参 -->
      <button @click="fn3($event,2)">按钮3</button>
    </div>
    <script>
      Vue.config.productionTip = false; // 阻止 Vue在启动时生成生产提示

      const vm = new Vue({
        el: "#root", // 挂载的容器
        data() {
          // 数据
          return {};
        },
        methods: {
          fn1(e) {console.log(e,'fn1');},
          fn2(e) {console.log(e,'fn2');},
          fn3(e,a) {console.log(e,a,'fn3');},
        },
      });
    </script>
  </body>
</html>
